If you're able to install stronger brakes in the rear in addition to Defender fronts, the hydraulic proportions are probably more balanced than before anyways. The next important key seems to be fitting a larger master.
I didn't read the whole thread but Red Winch makes bolt on brackets to slap front brakes in the rear.
It has more character?
By the way, those are not D1 front calipers. They have regular straight 10x1mm fitting, not banjo.
It is one more step in bastardization the truck. Not that I haven't taken any of the steps, but... 10x1 is something pretty simple to remember. I wanted to put together a D1/Classic brake line repair kit (a few 10x1 to -3 AN adapters, a couple of hoses of different lengths), but never got around to it.Red suggests swapping to a banjo fitting according to their site.